EDM 700 Fuel Flow error

[the400kid]

The setup is as follows: EDM 700 with Fuel Flow option, connected to a GTN 750.

I noticed during my last flight that the fuel flow was not displaying on the GTN, which is fed in from the EDM 700. When I cycle through the fuel flow displays on the '700, the last entry shows "NO COM". Nothing changed in terms of configuration on either unit.

Ideas?

 

[Ryan Klems]

Any work done to plane recently? Given that the GTN is not displaying fuel flow, and the EDM is showing no com, looks like both the TX and RX are no longer communicating. Perhaps a connector was dislodged? Any software updates performed the GTN750 (occasionally one of those can mess up configuration). Do you know how to boot the GTN to config mode and go to the RS232 configuration page? Can you post a photo?

 

[the400kid]

Any work done to plane recently? Given that the GTN is not displaying fuel flow, and the EDM is showing no com, looks like both the TX and RX are no longer communicating. Perhaps a connector was dislodged? Any software updates performed the GTN750 (occasionally one of those can mess up configuration). Do you know how to boot the GTN to config mode and go to the RS232 configuration page? Can you post a photo?

It just came out of annual, but no changes in terms of the panel or software updates. I should have mentioned that the fuel flow information is being displayed on the 700, it's just not getting to the GTN, or it's getting to the GTN but something has happened to its configuration.

Very perplexing.

 

[Ryan Klems]

Anything added during the annual like an ELT that they might have interfaced to the GTN?

With the FF showing on the 700, that would indicate that the FF pigtail connector is at least connected to the EDM. The Tx and Rx wires (white and gray twisted together) come off of the connector and go to the GTN. Sometimes there might be a secondary connector on those wires between the EDM and the GTN put in by the installer for various reasons.

The easiest thing to start with would be to check the config on the GTN, which you can do by holding the Home button while powering on the GTN. Carefully navigate to "GTN Setup" -> "RS-232" and look at the various port settings, see if one is configured for Aviation on the output and either FADC Format 1 or Fuel Format 2 for the input format (or just take a picture and post it here). That would at least determine if the configuration for some port is setup for communicating with the EDM. It would be best if you knew which port it was supposed to be configured on (any wiring diagrams from the install previously?). If you see that one of the ports is configured for fuel, you can tap the back button to get back to the home screen, then navigate to "GTN Diagnostics" -> "Serial Diagnostics", then tap the port key and select the port that you found configured for one of the fuel formats. Assuming the port is connected to something (that is powered on) you should see some sort of activity. Take a picture of that if there is activity of any sort, and post it here, it can be useful for seeing what data format is actually being transmitted in case there is a misconfiguration on the other side.

 

[the400kid]

Anything added during the annual like an ELT that they might have interfaced to the GTN?

With the FF showing on the 700, that would indicate that the FF pigtail connector is at least connected to the EDM. The Tx and Rx wires (white and gray twisted together) come off of the connector and go to the GTN. Sometimes there might be a secondary connector on those wires between the EDM and the GTN put in by the installer for various reasons.

The easiest thing to start with would be to check the config on the GTN, which you can do by holding the Home button while powering on the GTN. Carefully navigate to "GTN Setup" -> "RS-232" and look at the various port settings, see if one is configured for Aviation on the output and either FADC Format 1 or Fuel Format 2 for the input format (or just take a picture and post it here). That would at least determine if the configuration for some port is setup for communicating with the EDM. It would be best if you knew which port it was supposed to be configured on (any wiring diagrams from the install previously?). If you see that one of the ports is configured for fuel, you can tap the back button to get back to the home screen, then navigate to "GTN Diagnostics" -> "Serial Diagnostics", then tap the port key and select the port that you found configured for one of the fuel formats. Assuming the port is connected to something (that is powered on) you should see some sort of activity. Take a picture of that if there is activity of any sort, and post it here, it can be useful for seeing what data format is actually being transmitted in case there is a misconfiguration on the other side.

Thanks for the insight. I've been in the configuration before and can find my way around. I'm just hoping that the Fuel Format changed on its own. How that can happen, I have no idea.

 

[Ryan Klems]

Thanks for the insight. I've been in the configuration before and can find my way around. I'm just hoping that the Fuel Format changed on its own. How that can happen, I have no idea.

Yeah, I've not seen that happen other than when doing a software update. That's why I was wondering about perhaps upgrading to a 406 ELT and shop connecting that to the GPS and then fiddling around with the configuration. I've seen a JPI lose its configuration before, but on the 700 there is no setting for the input (the 730/830 does have an input setting), only the output, and the fact that it's saying "No Com" according to the JPI diagnostics means "Communications are received by EDM and the Auto-Protocol setup is in process. Verify correct output format setup in GPS receiver; check GPS connections." so would seem the config issue is on the GTN side.

 

[Jesse Saint]

If the EDM says No Com, and the GTN shows no fuel flow, then there is likely a connector between the two that has come unplugged, because the EDM should be getting information from the GTN but isn't, and the GTN should be getting information from the EDM but isn't.